Doping dependence of pseudogap and related charge dynamics in Nd2-xCexCuO4.

A notable pseudogap ( Delta(PG) as large as 0.2-0.4 eV) has been found below a characteristic temperature T(*) in the optical conductivity spectrum for metallic but nonsuperconducting crystals of Nd2-xCexCuO4 (x<0.15). The Delta(PG) and T(*) decrease with doping x, holding the relation of Delta(PG) approximately 10k(B)T(*). The Drude-like component is observed to evolve concomitantly with the pseudogap. The T(*) almost coincides with another characteristic temperature T0 that scales the Hall coefficient. These results indicate that the charge transport in the underdoped region is under the strong influence of the pseudogap state.